Preparation method of millet straw and sweet potato residue mixed silage

Abstract

The invention belongs to the field of feed processing, and particularly relates to a preparation method of millet straw and sweet potato residue mixed silage, which comprises the following steps: pretreatment of raw materials: chopping millet straw; mixing: according to a designed mixing ratio, weighing the chopped millet straws and fresh sweet potato residues after starch processing; filling: filling the uniformly mixed raw materials into a silage container, compacting, exhausting air, and sealing and storing; and storage: storing at normal temperature. The high-moisture grain residues and the low-moisture straws are mixed to realize synergistic ensiling, so that the respective raw material defects of the millet straws and the sweet potato residues can be effectively made up, and the high-quality silage which is excellent in fermentation quality, perfect in nutrition preservation and high in aerobic stability is ensured; and a reliable technical scheme is provided for realizing efficient and feed utilization of unconventional feed resources.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of feed processing, and particularly relates to a preparation method of mixed silage feed of millet straw and sweet potato residue. BACKGROUND

[0002] At present, the livestock industry in China is facing structural problems of feed resources, and the cost of conventional raw materials continues to rise. However, a large amount of unconventional resources such as straw and processing by-products have not been efficiently utilized. Developing such resources is of great significance to the development of grain-saving breeding industry. Millet straw, as a by-product of a grain-feeding crop, has the advantages of high crude protein content and low fiber content, and has good basic feed. However, it is difficult to compact when siloed alone due to its low water content and insufficient soluble carbohydrates, and harmful microorganisms are easy to breed, resulting in poor fermentation quality. Sweet potato residue, as the main by-product after extracting starch from sweet potato, is rich in residual starch and cellulose. However, its high moisture content leads to easy spoilage during storage and transportation, and it often emits sour and smelly odor, so it is often discarded as waste, causing resource waste and environmental pollution. SUMMARY

[0003] In order to solve the problems existing in the prior art, the application provides a preparation method of mixed silage feed of millet straw and sweet potato residue.

[0004] The specific technical scheme adopted by the application is: A preparation method of mixed silage feed of millet straw and sweet potato residue, comprising the following steps: S1. Pretreatment of raw materials: cutting millet straw; S2. Mixing: according to the designed mixing ratio, the cut millet straw and fresh sweet potato residue after starch processing are weighed; S3. Filling: the mixed raw materials are filled into a silo container, compacted, air excluded, and sealed for storage; S4. Storage and fermentation, and the fermentation temperature is 15-28℃, preferably 25±1℃.

[0005] The cutting length of the millet straw is 2-4cm, and the sweet potato residue is the solid by-product remaining after extracting starch from sweet potato.

[0006] The designed fresh weight ratio of the millet straw and the sweet potato residue is 1:3.

[0007] The designed storage time is 60 days.

[0008] The application has the following beneficial effects: The present application mixes high-moisture vinasse and low-moisture straw to realize synergistic ensiling, can effectively make up for the respective raw material defects of millet straw and sweet potato residue, ensure the fermentation quality of high-quality ensiled feed with excellent fermentation quality, perfect nutrient preservation and high aerobic stability, and provide a reliable technical solution for efficient and high-value utilization of non-conventional feed resources. DETAILED DESCRIPTION

[0009] The present application will be further described below in combination with specific examples: 1. EMBODIMENT The present application discloses a preparation method of millet straw and sweet potato residue mixed ensiled feed, comprising the following steps: S1. Raw material pretreatment: cutting millet straw; S2. Mixing: according to the designed mixing ratio, millet straw and fresh sweet potato residue after processing starch are weighed; S3. Filling: the mixed raw materials are filled into an ensiling container, compacted, air is removed, and sealed for storage; S4. Storage and fermentation.

[0010] 2. EXPERIMENTAL DESIGN The present application determines the mixing ratio of millet straw and sweet potato residue through an experimental method, and determines the fermentation time by mixing ensiling for different days, and the specific experimental steps are as follows: 2.1 Experimental materials and preparation The sweet potato residue is the solid residue remaining after sweet potato is processed into starch, and fresh sweet potato residue is collected after processing; millet straw of the same period is collected and cut to 2-4 cm.

[0011] The conventional nutrient quality of millet straw and sweet potato residue raw materials is determined. According to the quality of the raw materials, millet straw and sweet potato residue are mixed uniformly according to a ratio of 1:3 (fresh weight basis), and the moisture content is controlled to be about 65%. The ensiling time is 0, 3, 7, 15, 30, 60 and 90 days (a total of 7 treatments), and after sufficient mixing, they are filled into an ensiling container, compacted to remove air, and sealed for storage. The fermentation temperature is 15-28℃, preferably 25±1℃.

[0012] 2.2 Analysis of conventional nutrient components After the fermentation is completed, the ensiling container is opened in a sterile operation table, and about 500 g of ensiled samples are randomly collected from different parts. The dried samples are used for conventional nutrient quality determination. Including dry matter (DM), crude protein (CP), crude ash (Ash), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude fat (EE) and the like.

[0013] 2.3 Determination of fermentation quality index and aerobic stability At the end of fermentation, the silage container was opened in a sterile operating table, and about 500 g of fresh silage sample was randomly collected from different parts for fermentation index detection, including pH, ammonia nitrogen (NH3-N), lactic acid (LA), acetic acid (AA), propionic acid (PA), and butyric acid (BA) content, to systematically evaluate the fermentation quality.

[0014] 2.4 Aerobic stability evaluation 1 kg of silage sample was weighed and placed in a 2 L polyethylene silage tank, and the tank opening was covered with double gauze to control excessive moisture loss and avoid foreign matter contamination, and was placed at room temperature (25±1℃). A USB temperature and humidity data logger was used to automatically collect silage center temperature every 30 minutes, and two indoor control point temperatures were monitored simultaneously. When the center temperature of the silage sample was consistently 2℃ higher than the average indoor temperature, it was determined that the aerobic stability endpoint had been reached, indicating that aerobic spoilage had begun to occur.

[0015] 2.5 Membership function value calculation Twelve core indicators (DM, CP, NDF, ADF, Ash, EE, pH, LA, AA, PA, NH3-N, and aerobic stability) were selected for membership function analysis. The indicators positively correlated with feed nutrition and fermentation quality were positive indicators, and the indicators negatively correlated with feed nutrition and fermentation quality were negative indicators. The membership degree of each indicator was obtained, and the total membership degree of each mixed silage was calculated. The total membership degree value was used as the basis for ranking the comprehensive value of mixed silage (the larger the total membership degree value, the higher the comprehensive value).

[0016] 2.6 Microbial community diversity and composition determination The containers were opened at 0, 3, 7, 15, 30, 60, and 90 days, and 5 g of mixed silage sample was immediately taken and placed in a 5 mL cryogenic tube, with 5 replicates for each treatment group. The samples were stored in a -80℃ freezer for sequencing. The succession pattern of microbial community during mixed silage fermentation was analyzed using 16S rRNA gene high-throughput sequencing technology, and the appropriate silage time was selected.

[0017] 2.7 In vitro gas production determination The AGRS-Ⅲ type 64 channel microbial fermentation trace gas production automatic recording device was used for in vitro gas production culture. The fermented 60-day millet straw and sweet potato residue mixed silage feed was used to replace the yellow silage feed at different proportions (100%, 70%, 50%, 30%, 0%) to conduct in vitro gas production test. 0.5 g of silage sample was weighed and placed in a 150 mL anaerobic fermentation bottle. The fermentation bottle was placed in a 39℃ constant temperature incubator for preheating. 50 mL of buffer and 25 mL of fresh rumen fluid filtered through four layers of gauze were added to the bottle. After connecting the CO2 exhaust pipe, the bottle was immediately sealed with a corresponding sensor connected to the gas production device. The whole process was carried out in a 39℃ water bath. After placing in the constant temperature incubator, it was continuously cultured for 72 hours. The gas production was recorded at 3, 6, 9, 12, 24, 36, 48, 72 hours, and a blank tube without substrate was set up for calibration.

[0018] 3 Test results 3.1 Determine the mixing ratio of millet straw and sweet potato residue silage Through the detection of nutritional quality, the dry matter content of millet straw before fermentation was 90.2%, the crude protein content was 4.48%, the neutral detergent fiber content was 65.44%, the acid detergent fiber content was 43.35%, and the crude ash content was 6.88%. The dry matter content of sweet potato residue was 15.58%, the crude protein content was 2.84%, the neutral detergent fiber content was 15.87%, the acid detergent fiber content was 12.58%, and the crude ash content was 3.15%. Based on the principles of silage technology and the comprehensive consideration of the nutritional characteristics of raw materials, the mixing ratio of millet straw to sweet potato residue was 1:3 (fresh weight ratio) according to the calculation of silage dry matter content of 30-35%.

[0019] 3.2 Nutritional components of mixed silage at different fermentation times Through the comprehensive evaluation of millet straw and sweet potato residue mixed silage samples at different fermentation days, including sensory evaluation and routine nutritional component analysis, it was found that the dry matter content of mixed silage fermented for 0-30 days was between 32.87-32.93%, and the dry matter content reached a peak (35.95%) when fermented for 60 days, which was significantly higher than that of other days (especially when fermented for 90 days, the dry matter content was 30.83%), indicating that the best fermentation efficiency and nutrient preservation were achieved at 60 days. The neutral detergent fiber content was 52.59% after 30 days of fermentation, and remained stable for 60 days and 90 days. The acid detergent fiber content was 30.94% after 15 days of fermentation, and then entered a plateau period until 90 days, with no significant change. Meanwhile, the crude protein, crude fat and crude ash contents remained stable. These results showed that the mixed silage fermented for 60 days had a comprehensive advantage in nutritional quality. The significant decrease in dry matter content of the 90-day fermentation group indicated that the increased nutrient loss caused by excessive fermentation time.

[0020] 3.3 Fermentation quality of mixed silage at different fermentation time The dynamic changes of fermentation quality revealed the whole process of silage maturation. The analysis of mixed silage fermentation quality showed that the first 30 days of fermentation was a rapid acidification period, with pH dropping to 3.64 and lactic acid reaching a peak (0.46). However, the key quality optimization occurred during the subsequent stabilization period (30-60 days). Although the lactic acid content moderately declined from the peak, the pH slightly increased to 3.88, the ammonia nitrogen dropped to the lowest, indicating that protein decomposition was maximally inhibited. Meanwhile, the butyric acid content (0.02) was the lowest, and the acetic acid (0.34) maintained a high level, laying a good foundation for aerobic stability. By the 90th day of fermentation, the pH further increased with a significant decrease in lactic acid, indicating signs of over-fermentation.

[0021] Based on the comprehensive evaluation of membership function method, the total membership value was used to rank the treatments. The results showed that the comprehensive value of millet straw and sweet potato residue mixed silage at different fermentation time was ranked as: 60 days > 7 days > 15 days > 0 days > 30 days > 3 days > 90 days, and the optimal fermentation time was preliminarily determined as 60 days.

[0022] 3.4 Effect of fermentation time on microbial community structure of mixed silage Based on 16S rRNA gene high-throughput sequencing technology, the structure and dynamic changes of microbial community in millet straw and sweet potato residue mixed silage at different fermentation time were analyzed. The coverage index of all samples reached more than 0.99, indicating that the sequencing depth was sufficient to reflect the true situation of microbial community in the samples. Alpha diversity analysis showed that the Ace index, Chao1 index, Shannon index and Simpson index of mixed silage fermented for 60 days were significantly lower than those of other days, indicating that the bacterial species richness and community diversity of this group were the lowest.

[0023] At the level of phylum classification, the dominant bacterial phylum composition of each fermentation time treatment group was highly consistent, mainly including Firmicutes ( Firmicutes ), Proteobacteria ( Proteobacteria ), Actinobacteria ( Actinobacteriota ) and Bacteroidetes ( Bacteroidota ), accounting for more than 98% of the total community. Among them, Firmicutes ( Firmicutes ) was the first dominant phylum in all fermentation time, and its relative abundance was the highest at 60 days (98.20%) and 90 days (98.24), which contributed to the excellent fermentation quality and long-term stable preservation of mixed silage.

[0024] Further analysis at the genus level revealed the succession rules of key bacterial groups closely related to the silage fermentation process. The main genera included Lactobacillus ( Lactobacillus ), Leuconostoc (Leuconostoc Lactococcus spp. Lactococcus ), Pediococcus ( Pediococcus ), Enterobacteriaceae ( Enterobacter ) and Weissella spp. Weissella ) etc. Lactobacillus ( Lactobacillus As a core representative of homofermentative lactic acid bacteria, its relative abundance reached its peak at 60 days of fermentation (81.48%), significantly higher than all other groups. This is consistent with the lowest pH value and highest lactic acid content in this group. *Leuconostoc* genus ( Leuconostoc As a typical heterofermentative lactic acid bacteria, *Lactobacillus* constituted a relatively high proportion in the early stages of fermentation (64.25% at day 0). However, its relative abundance was significantly suppressed at 60 days (10.35%) and 90 days (11.68%). Microbial community analysis showed that fermentation time significantly affected the silage microbial community structure. At 60 days of fermentation, the community exhibited low diversity and high specificity, characterized by the presence of *Lactobacillus* spp. Lactobacillus The absolute dominant position of Leuconostoc ( ) and the genus Leuconostoc Leuconostoc Other genera, represented by ), were suppressed.

[0025] 3.5 Evaluation of the combined effect of mixed silage replacing yellow silage using in vitro gas production method A comprehensive analysis of in vitro gas production data for different feed combinations at each time point (3, 6, 9, 12, 24, 36, 48, and 72 hours) revealed that the combination of replacing all silage with a 60-day fermented mixed silage exhibited the highest or near-highest gas production at all time points, and was significantly higher than other combinations at most time points (after 12 hours). The mixed silage replacing 70% silage showed no significant difference in gas production compared to the full replacement group at multiple time points (6, 9, 12, 24, 36, 48, and 72 hours). Compared to the 50% silage replacement group, the 50% silage replacement group showed a significant decline in gas production performance starting from the 9th hour, while the 30% silage replacement group showed a sustained and significant inhibition as early as the 6th hour.

[0026] 4. Conclusion 4.1 This invention clarifies the optimal ratio and fermentation cycle for mixed silage of millet straw and sweet potato residue: based on the quality of the raw materials, millet straw and sweet potato residue are mixed evenly at a ratio of 1:3 (fresh weight ratio). This ratio can effectively coordinate the dry matter content and moisture distribution of the raw materials. Combining nutritional quality and fermentation quality, different fermentation times for mixed silage are comprehensively evaluated, and it is determined that 60 days of fermentation is the optimal silage cycle. Under this condition, high-quality silage with pure aroma, bright color, uniform texture, complete nutrient preservation, and stable fermentation quality can be obtained.

[0027] 4.2 Based on 16S rRNA sequencing analysis, it was determined that the microbial community of the mixed silage of millet straw and sweet potato residue fermented for 60 days exhibited the genus *Lactobacillus* (…). Lactobacillus The relative abundance of the bacteria was significantly the highest, while the community alpha diversity was reduced to the lowest level. This specific structure, dominated by homozygous fermenting lactic acid bacteria, drives efficient and stable lactic acid fermentation, resulting in suitable pH and minimal ammonia nitrogen production at the biochemical level, ultimately achieving the highest nutrient retention rate and optimal overall fermentation quality.

[0028] 4.3 Comparison of in vitro fermentation gas production after mixing silage and yellow silage in different proportions shows that replacing all yellow silage with silage fermented for 60 days resulted in the highest or near-highest gas production of roughage at all time points, and significantly higher than other combinations at most time points (after 12 hours). Therefore, 60-day fermented silage is not a simple replacement, but effectively improves the quality of roughage. It can completely replace yellow silage and exhibits the highest gas production, proving that this silage is a more efficient energy feed source than the original yellow silage, with higher feed value and substitution potential.

[0029] 4.4 The core advantage of this invention lies in its innovative use of inexpensive sweet potato residue and millet straw. Through the efficient complementarity of their physical properties (straw absorbs excess moisture from the sweet potato residue to quickly create a suitable fermentation environment) and nutritional properties (sweet potato residue provides fermentation sugars, while straw provides physical structure and a durable substrate), a high-quality endogenous fermentation system requiring no additional additives is constructed. This method not only fundamentally solves the industrialization problem of high-moisture sweet potato residue's susceptibility to spoilage and difficulty in storage at extremely low cost, but also directly produces high-quality silage with excellent fermentation quality, complete nutrient preservation, and strong aerobic stability. It provides a simple, economical, and feasible technological path for the large-scale and feed utilization of these two agricultural by-products.

Claims

1. A method for preparing silage from a mixture of millet straw and sweet potato residue, characterized in that: Includes the following steps: S1. Raw material pretreatment: Chop the millet straw; S2. Mixing: Weigh out the chopped millet straw and fresh sweet potato residue after starch processing, according to the designed mixing ratio; S3. Filling: Fill the silage container with the well-mixed raw materials, compact them, remove the air, and seal for storage; S4. Storage and fermentation, with a storage temperature range of 15-28℃.

2. The method for preparing silage from a mixture of millet straw and sweet potato residue according to claim 1, characterized in that: The millet straw is chopped to a length of 2-4 cm, and the sweet potato residue is the solid byproduct remaining after starch extraction from sweet potatoes.

3. The method for preparing silage from a mixture of millet straw and sweet potato residue according to claim 1, characterized in that: The design mixing ratio of millet straw and sweet potato residue is 1:3 based on fresh weight.

4. The method for preparing silage by mixing millet straw and sweet potato residue according to claim 1, characterized in that: The storage period is designed to be 60 days.

5. The method for preparing silage by mixing millet straw and sweet potato residue according to claim 1, characterized in that: The storage temperature is 25±1℃.